Already got a bigger exhaust.
I also have a...
Big bore kit taking it from 43cc to 49cc
Ported, polished enlarged alloy intake manifold (kept cracking the plastic ones with the extra power!)
Ported intakes.
I've advanced the ignition timing
I have a high performance 16mm carb (12mm standard)
I have an enlarged velocity stack
A K&N filter
High flow fuel filter.
My engine is not a reed type, and I have installed every standard method of upping the power. Its now running at double the speed and power than it did when I got it.
Now I'm thinking of adding this kit although I'm not sure how much power gains it would give me over the kit I already have.
However I may get it to try another idea I have. If I strip off some of the cooling fins, and manage to surround some of the head with water, I could then re route the air from the fly wheel into the intake. This should work like a supercharger.